Repair of through-hole damage using braze sintered preform

ABSTRACT

A method may include removing a portion of a base component adjacent to a damaged portion of the base component to define a repair portion of the base component. The base component may include a cobalt- or nickel-based superalloy, and the repair portion of the base component may include a through-hole extending from a first surface of the base component to a second surface of the base component. The method also may include forming a braze sintered preform to substantially reproduce a shape of the through-hole. The braze sintered preform may include a Ni- or Co-based alloy. The method additionally may include placing the braze sintered preform in the through-hole and heating at least the braze sintered preform to cause the braze sintered preform to join to the repair portion of the base component and change a microstructure of the braze sintered preform to a brazed and diffused microstructure.

This application is a continuation of U.S. patent application Ser. No.16/272,664, filed Feb. 11, 2019, the entire content of which isincorporated by reference herein.

TECHNICAL FIELD

The present disclosure generally relates to techniques for repairingalloy components.

BACKGROUND

Some articles formed from superalloys include equiaxed, directionallysolidified, or a single crystal alloys and are formed using casting.Replacement of such articles in case of damage may be expensive, butrepair of such articles may be difficult, particularly when damage tothe article is significant in size or extends through a thickness of aportion of a component.

SUMMARY

In some examples, the disclosure describes a method including removing aportion of a base component adjacent to a damaged portion of the basecomponent to define a repair portion of the base component. The basecomponent may include a cobalt- or nickel-based superalloy, and therepair portion of the base component may include a through-holeextending from a first surface of the base component to a second surfaceof the base component. The method also may include forming a brazesintered preform to substantially reproduce a shape of the through-hole.The braze sintered preform may include a Ni- or Co-based alloy. Themethod additionally may include placing the braze sintered preform inthe through-hole and heating at least the braze sintered preform tocause the braze sintered preform to join to the repair portion of thebase component and change a microstructure of the braze sintered preformto a brazed and diffused microstructure.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a conceptual and schematic diagram illustrating an examplerepaired article including a base component, a repair portion, and abraze sintered preform that substantially fills the repair portion.

FIG. 1B is a conceptual and schematic diagram illustrating an examplerepaired article including a base component having three-dimensionalfeatures on a surface of the base component, a repair portion, and abraze sintered preform that substantially fills the repair portion andhas three-dimensional features on a surface of the braze sinteredpreform.

FIG. 2 is a flow diagram illustrating an example technique for repairinga damaged portion including a through-hole using a BSP material.

FIGS. 3A-3J are photographs illustrating an example nozzle guide vaneduring various stages of repair of a damaged vane airfoil.

FIGS. 4A-4D are photographs illustrating an example nozzle guide vaneduring various stages of repair of a damaged platform.

FIGS. 5A and 5B are photographs illustrating an example BSP materialhaving three-dimensional surface features and a repaired vane airfoilincluding the BSP material having the three-dimensional surfacefeatures.

DETAILED DESCRIPTION

This disclosure describes assemblies, systems, and techniques forrepairing through-hole damage to an alloy component using a brazesintered preform (BSP) material. The BSP material may include a a Ni- orCo-based alloy and may include a powder or mixture of powders that hasbeen sintered to reduce porosity of the braze material. The BSP materialmay facilitate repair of larger damaged portions of an article than abraze paste or loose braze powder, damaged portions that extend througha thickness of at least a portion of the article, or both. In someexamples, the BSP material may be used to repair equiaxed, directionallysolidified, or single-crystal Ni-based alloys or Co-based alloys, suchas those used in nozzle vane guides of gas turbine engines or the like.

The BSP material may be formed or shaped to substantially fill a repairportion of the damaged article. As used herein, “substantially fill”refers to a BSP material that fills all or nearly all the repair portionof the damaged article, aside from cracks or spaces at the interfacebetween the BSP material and the article adjacent to the repair portion.In some examples, additional braze material, such as a braze paste or anadditional BSP material, may be placed adjacent to the BSP material thatsubstantially fills the repair portion to fill or cover the damage thatthe BSP material does not fill, such as the cracks or spaces.

In this way, the BSP material and optional additional braze material maybe used to repair damage to an article and may substantially fill therepair portion of the article. The BSP material may be used withequiaxed, directionally solidified, or single-crystal Ni-based alloy orCo-based alloy articles and may result in repaired articles in which therepaired portion may have metallurgical properties substantially similarto those of the original article. In this way, larger damaged portionsof equiaxed, directionally solidified, or single-crystal Ni-based alloyor Co-based alloy articles may be repaired using the described BSPmaterial than a braze paste or powder.

FIG. 1A is a conceptual and schematic diagram illustrating an examplerepaired article 10 including a base component 12, a repair portion 14,and a braze sintered preform 16 that substantially fills repair portion14. In some examples, repaired article 10 may be used as part of a hightemperature mechanical system. For example, repaired article 10 may beor be part of a nozzle guide vane (NGV) that is used in a high pressureor intermediate pressure stage turbine in a gas turbine engine. In otherexamples, repaired article 10 may include another component of a hightemperature mechanical system, such as another component of a gasturbine engine. For example, the article may include a gas turbineengine blade, gas turbine engine vane, blade track, combustor liner,honeycomb, or the like.

Base component 12 may include a metal or alloy. In some examples, basecomponent 12 may include a Ni- or Co-based superalloy. Base component 12may be formed from a polycrystalline alloy, a directionally solidifiedalloy, or a single crystal alloy. Base component 12 may include otheradditive elements to alter its mechanical and chemical properties, suchas toughness, hardness, temperature stability, corrosion resistance,oxidation resistance, and the like, as is known in the art. Any usefulsuperalloy may be utilized in base component 12, including, for example,Ni-based alloys available from Martin-Marietta Corp., Bethesda, Md.,under the trade designation MAR-M246, MAR-M247; Ni-based alloysavailable from Cannon-Muskegon Corp., Muskegon, Mich., under the tradedesignations CMSX-3, CMSX-4, CMSX-10, and CM-186; Co-based alloysavailable from Martin-Marietta Corp., Bethesda, Md., under the tradedesignation MAR-M509; Ni-based alloys available from Special MetalsCorporation, New Hartford, N.Y. under the trade designation INCONEL™738, INCONEL™713; and the like. The compositions of CMSX-3 and CMSX-4are shown below in Table 1.

TABLE 1 CMSX-3 CMSX-4 (wt. %) (wt. %) Cr 8 6.5 Al 5.6 5.6 Ti 1 1 Co 5 10W 8 6 Mo 0.6 0.6 Ta 6 6 Hf 0.1 0.1 Re 3 Ni Balance Balance

Base component 12 may be made using at least one of casting, forging,powder metallurgy, or additive manufacturing.

Although FIG. 1 illustrates base component 12 as defining a simple,substantially rectangular geometry, in other examples, base component 12may define a more complex geometry, including simple or complex curves,overhangs, undercuts, internal cavities, or the like. Examples of basecomponent 12 that are part of a nozzle guide vane are shown in FIGS.3A-6B.

Base component 12 has been damaged. The damage may extend through athickness of base component 12 from first surface 22 to second surface24. The damage may include, for example, airfoil burn-through, platformburn-through, trailing edge burn out, trailing edge burn back, leadingedge burn out, a through crack, a turbine vane internal pedestal damage,blow-out failure of pressure and/or suction sides of an airfoil, foreignobject damage, corrosion, or the like. As such, the damage may define athrough-hole through a portion of base component 12 extending from firstsurface 22 to second surface 24. As shown in FIG. 1A, a damaged portionof base component 12 has been worked or machined to remove at least partof the damaged portion, defining repair portion 14. Repair portion 14defines a through-hole through a portion of base component 12 andextends from first surface 22 to second surface 24. Compared to thedamaged portion, repair portion 14 defines smoother and/or geometricallysimpler repair surfaces 18 and 20 against which BSP material 16 may bepositioned. This may facilitate contact between surfaces of repairportion 14 and BSP material 16. FIG. 1 illustrates repair surfaces 18and 20 as substantially flat surfaces. In other examples, repairsurfaces 18 and 20 may define other, more complex shapes, including, forexample, simple or complex curves, overhangs, undercuts, or the like.

BSP material 16 is positioned in repair portion 14 and contacts repairsurfaces 18 and 20. BSP material 16 includes a Ni- or Co-based alloy andmay include a powder mixture that has been sintered to form a preform.Sintering may reduce porosity compared to the powder, which may reduceporosity in the repaired portion during and after repair.

BSP material 16 may include a predetermined shape. The predeterminedshape may be selected to substantially fill repair portion 14 throughsubstantially an entire depth of repair portion 14 (e.g., from firstsurface 22 to second surface 24). The predetermined shape may beselected after machining or working base component 12 to remove at leastpart of the damaged portion of base component 12 to define repairportion 14. For example, after removal of the at least part of thedamaged portion, repair portion 14 may be imaged or otherwiseinterrogated to determine the shape of repair portion 14. BSP material16 may then be shaped or formed to substantially match the shape ofrepair portion 14. Alternatively, repair portion 14 may be formed tosubstantially match a predefined shape of BSP material 16.

BSP material 16 may be made by forming or shaping a powder or paste intothe predetermined shape (e.g., in a mold), then at least partiallysintering the formed or shaped powder or paste to form BSP material 16.In this way, the shape of BSP material 16 may be tailored to the shapeof repair portion 14.

In some examples, as shown in FIG. 1B, a repaired article may include abase component that defines a more complicated shape, such asthree-dimensional surface features. FIG. 1B is a conceptual andschematic diagram illustrating an example repaired article 30 includinga base component 32 having three-dimensional features 46 on a surface 44of the base component 32, a repair portion 34, and a BSP material 36that substantially fills the repair portion 34 and has three-dimensionalfeatures 48 on a surface of the BSP material. Like base component 12 ofFIG. 1A, base component 32 of FIG. 1B defines a repair portion 34including repair surfaces 38 and 40. Base component 32 also defines afirst surface 42 and a second surface 44.

Unlike base component 12 of FIG. 1A, base component 32 is not the onlypart of repaired article 30. Repaired article 30 also includes a secondcomponent 50 to which base component 32 is attached or joined. Forexample, repaired article 30 may be a turbine nozzle guide vanecomponent in which base component 32 is a pressure side airfoil wall,second component 50 is a suction side airfoil wall, andthree-dimensional surface features 46 on airfoil inner surface 44 ofbase component 32 are pedestals, cooling features, or the like. Asanother example, repaired article 30 may be a dual wall component inwhich base component 32 is an outer wall, second component 50 is aninner wall or spar, and three-dimensional surface features 46 on innersurface 44 of base component 32 are pedestals, cooling features, or thelike. The damaged portion and repair portion 34 define a through-holeextending through base component 32 from first surface 42 to secondsurface 44, but may or may not extend through second component 50.

Unlike base component 12 of FIG. 1A, second surface 44 of base component32 defines three-dimensional surface features 46, such as coolingfeatures, pedestals or stand-offs, or the like. The damaged portion ofbase component 32 may have included similar three-dimensional surfacefeatures 46. As such, in order to fully repair the damaged portion ofbase component 32, BSP material 36 may be formed to includesubstantially similar three-dimensional features 48 on a surface of BSPmaterial 36 that is placed adjacent to (e.g., parallel with) secondsurface 44 of base component 32. The three-dimensional features may beformed during the sintering process or after the sintering process usinga machining process such as milling, grinding, waterjet, laser,electrodischarge machining, or the like. By including three-dimensionalfeatures 48, BSP material 36 may substantially fill repair portion 34and may replace substantially all of the damaged portion of basecomponent 32.

BSP material 16 and BSP material 36 (referred to collectively as “BSPmaterial 16”) may include a Ni-based or Co-based alloy. In someexamples, BSP material 16 may include greater amounts of alloyingelements that some other braze materials used in braze foils, which maycontribute to improved mechanical properties, chemical properties, orboth compared to some other braze materials used in braze foils. Forexample, BSP material 16 may possess sufficient mechanical strength andhigh temperature oxidation resistance to be used in a nozzle guide vanein a gas turbine engine.

In some examples, BSP material 16 may include both a braze alloy powder(e.g., a relatively low-melt powder composition) and a superalloy powder(e.g., a relatively high-melt powder composition). The low-melt alloypowder composition is an alloy, or a mixture of alloys, thatsubstantially melts below the braze temperature (hence the name“low-melt” or “braze powder”). In contrast, the high-melt alloy powdercomposition is an alloy, or a mixture of alloys, that remainssubstantially unmelted at the braze temperature, because the compositionhas a melting temperature above the braze temperature (hence the name“high-melt” or “superalloy powder”). In some implementations, the brazealloy powder and the superalloy powder may have specific powder meshsizes, and may be produced by induction melting the braze alloy or thesuperalloy powder, respectively, in vacuum or an argon atmosphere,followed by argon gas atomization. Each individual powder component usedin BSP material 16 may be analyzed to confirm the particle size andchemical compositions.

In some examples, the low-melt powder composition includes an alloy or amixture of alloys that melt at a temperature below about 1240° C. (about2265° F.), with the alloy or mixture of alloys being selected so thatthe low-melt powder composition as a whole substantially melts at atemperature between about 1093° C. (about 2000° F.) and about 1204° C.(about 2200° F.). The high-melt alloy powder composition may include asingle high-melt alloy or a mixture of alloys that melts at atemperature of greater than about 1315° C. (about 2400° F.).

In some examples, the low-melt powder composition may include one ormore alloy powders and includes between about 50 wt. % and about 70 wt.% Ni, between about 8 wt. % and about 20 wt. % Cr, between about 8 wt. %and about 15 wt. % Ta, between about 4 wt. % and about 10 wt. % Co,between about 2 wt. % and about 7 wt. % Al, up to about 2.25 wt. % B,and up to about 2.25 wt. % Si, and has a compositional melting range ofbetween about 1093° C. (about 2000° F.) and about 1240° C. (about 2265°F.). In some examples, the low-melt powder composition also includes upto about 1 wt. % each of at least one of Ti, W, Mo, Re, Nb, Hf, Pd, Pt,Jr, Ru, C, Si, P, Fe, Ce, La, Y, or Zr. In some examples the low-meltalloy powder comprises a mixture of two or more low-melt alloys. Forexample, a low-melt alloy powder may include (a) about 35% of a firstlow-melt powder including about 74 wt. % Ni, about 6 wt. % Cr, about 6wt. % Al, about 12 wt. % Co, and about 2 wt. % B, with a liquidustemperature of about 1121° C. (about 2050° F.); (b) about 45% of asecond low-melt powder including about 42 wt. % Ni, about 31 wt. % Cr,about 26 wt. % Ta, and about 1 wt. % B, with a liquidus temperature ofabout 1240° C. (about 2265° F.); and (c) about 20 wt. % of a thirdlow-melt powder including about 64 wt. % Ni, about 6 wt. % Al, about 8wt. % Co, about 4 wt. % W, about 4 wt. % Ta, about 3 wt. % Si, about 1wt. % Re, about 1 wt. % Nb, and about 1 wt. % B, with a liquidustemperature of about 1093° C. (about 2000° F.).

In some examples, the high-melt powder composition may include an alloyor mixture of alloys with a chemistry that is the similar to orsubstantially the same (e.g., the same or nearly the same) as the alloyin first component 12, second component 14, or both. For example, insome implementations, to join a first component 12 and a secondcomponent 14 that include Ni-based superalloy components such as thosemade of MAR-M246 or 247 or 002, or CMSX-3 or -4, the high-melt powdercomposition may include between about 50 wt. % and about 70 wt. % Ni,between about 2 wt. % and about 10 wt. % Cr, between about 2 wt. % andabout 10 wt. % Ta, between about 5 wt. % and about 15 wt. % Co, betweenabout 2 wt. % and about 10 wt. % Al, between about 2 wt. % and about 10wt. % W, between about 2 wt. % and about 4 wt. % Re, up to about 3 wt. %Mo, and up to about 3 wt. % Hf. In some examples, the high-melt powdercomposition also may include up to about 1 wt. % each of at least one ofTi, Nb, C, B, Si, or Zr. In some examples, the high-melt powdercomposition includes between about 55 wt. % and about 60 wt. % Ni, about7 wt. % Cr, about 6 wt. % Ta, about 12 wt. % Co, about 6 wt. % Al, about3 wt. % Re, about 1.5 wt. % Hf, and about 5 wt. % W.

The low-melt powder composition and the high-melt powder composition maybe combined in any selected ratio. In some examples, BSP material 16 mayinclude a powder mixture consisting of between about 20 wt. % and about80 wt. % low-melt powder composition and a balance high-melt powdercomposition (a ratio of between about 1:4 and about 4:1low-melt:high-melt powder). In some cases, braze alloy powder may be amixture of more than one braze alloys which are all powder. In someexamples, the ratio may be between about 1:3 and about 3:1low-melt:high-melt powder, such as a ratio between about 1:2 and about2:1 low-melt:high-melt powder, or a ratio between about 1:1 and about1:1.5 low-melt:high-melt powder. For example, BSP material 16 mayinclude between about 40 wt. % and about 50 wt. % low-melt alloy powderand between about 50 wt. % and about 60 wt. % high-melt powder, such asabout 45 wt. % low-melt alloy powder and about 55 wt. % high-meltpowder.

Hence, in some examples, BSP material 16 may include between about 50wt. % and about 90 wt. % Ni, up to about 15 wt. % Cr, up to about 10 wt.% Ta, up to about 10 wt. % Co, up to about 7 wt. % Al, up to about 4 wt.% W, up to about 2 wt. % Re, up to about 1 wt. % Mo, up to about 1 wt. %Hf, and, optionally, up to about 0.5 wt. % Nb, up to about 3 wt. % Si,and up to about 3 wt. % B. In some examples, BSP material 16 may includebetween about 50 wt. % and about 70 wt. % Ni, between about 10 wt. % andabout 15 wt. % Cr, between about 8 wt. % and about 10 wt. % Ta, betweenabout 8 wt. % and about 10 wt. % Co, between about 4 wt. % and about 7wt. % Al, between about 2 wt. % and about 4 wt. % W, between about 1 wt.% and about 2 wt. % Re, about 1 wt. % Mo, about 1 wt. % Hf, and,optionally, up to about 1% each at least one of Ti, Nb, Pd, Pt, Ir, Ru,C, B, Si, P, Mn, Fe, Ce, La, Y, or Zr. In some examples, BSP material 16may include between about 50 wt. % and about 70 wt. % Ni, between about10 wt. % and about 15 wt. % Cr, between about 8 wt. % and about 10 wt. %Ta, between about 8 wt. % and about 10 wt. % Co, between about 4 wt. %and about 7 wt. % Al, between about 2 wt. % and about 4 wt. % W, betweenabout 1 wt. % and about 2 wt. % Re, between about 0.5 wt. % and about 1wt. % Mo, between about 0.5 wt. % and about 1 wt. % Hf, between about0.1 wt. % and about 0.5 wt. % Nb, between about 0.05 wt. % and about 3wt. % Si, and between about 0.5 wt. % and about 2 wt. % B. In someexamples, BSP material 16 may include about 58 wt. % Ni, about 11 wt. %Cr, about 9 wt. % Ta, about 9 wt. % Co, about 5 wt. % Al, about 3 wt. %W, about 1 wt. % Mo, about 1 wt. % Re, and about 1 wt. % Hf; or mayinclude between about 10.2 wt. % and about 11.3 wt. % Cr, between about4.8 wt. % and about 5.1 wt. % Al, between about 9.1 wt. % and about 9.8wt. % Co, between about 2.8 wt. % and about 3.3 wt. % W, between about0.7 wt. % and about 0.9 wt. % Mo, between about 8.2 wt. % and about 8.8wt. % Ta, between about 0.6 wt. % and about 0.8 wt. % B, about 0.3 wt. %Si, between about 1.5 wt. % and about 1.8 wt. % Re, between about 0.8wt. % and about 0.9 wt. % Hf, between about 0.1 wt. % and about 0.2 wt.% Nb, and a balance Ni.

BSP material 16 may include between 0.05 and 0.116 wt. % C, between 0.11and 0.376 wt. % Si, between 8.424 wt. % and 11.640 wt. % Cr, between0.284 wt. % and 0.835 wt. % B, between 4.8 wt. % and 5.8 wt. % Al,between 2.675 wt. % and 4.232 wt. % W, between 0.650 wt. % and 1.362 wt.% Mo, between 1.4 wt. % and 2.462 wt. % Re, between 7.184 wt. % and8.942 wt. % Ta, between 0.690 wt. % and 1.386 wt. % Hf, and between8.725 wt. % and 10.964 wt. % Co, and a balance Ni. Additionally andoptionally, BSP material 16 may include a maximum of 0.082 wt. % Mn, amaximum of 0.003 wt. % S, a maximum of 0.013 wt. % P, a maximum of 0.018wt. % Ti, a maximum of 0.161 wt. % Y, a maximum of 0.034 wt. % Zr, amaximum of 0.180 wt. % Fe, a maximum of 0.093 wt. % V, a maximum of 0.10wt. % Cu, a maximum of 0.007 wt. % Mg, a maximum of 0.084 wt. % O, amaximum of 0.030 wt. % N, a maximum of 0.242 wt. % P, and a maximum of0.150 wt. % other elements.

BSP material 16 may include about 0.3 wt. % Si, about 11.4 wt. % Cr,about 0.8 wt. % B, about 4.9 wt. % Al, about 2.8 wt. % W, about 0.8 wt.% Mo, about 1.5 wt. % Re, about 52 wt. % Ni, about 0.2 wt. % Nb, about8.8 wt. % Ta, about 0.8 wt. % Hf, and about 9 wt. % Co. As anotherexample, BSP material may include about 0.3 wt. % Si, about 10.2 wt. %Cr, about 0.6 wt. % B, about 5.2 wt. % Al, about 3.3 wt. % W, about 0.9wt. % Mo, about 1.8 wt. % Re, about 52.1 wt. % Ni, about 0.2 wt. % Nb,about 8.1 wt. % Ta, about 1.0 wt. % Hf, and about 9.6 wt. % Co. Asanother example, BSP material 16 may include about 0.2 wt. % Si, about8.6 wt. % Cr, about 0.3 wt. % B, about 5.7 wt. % Al, about 4.1 wt. % W,about 1.2 wt. % Mo, about 2.3 wt. % Re, about 52.2 wt. % Ni, about 0.1wt. % Nb, about 7.3 wt. % W, about 1.2 wt. % Hf, and about 10.7 wt. %Co. Such alloys may be well suited for repairing single crystal Ni-basedsuperalloys, such as those used in nozzle guide vanes of gas turbineengines.

In selecting the proportions of components used in BSP material 16,higher weight percentages of high-melt powder may provide bettermechanical properties in view of their reduced levels of boron, silicon,or both. Conversely, higher percentages of low-melt powders may provideimproved braze flow. A proper balance between mechanical properties andbraze flow should be selected.

In some examples, BSP material 16 that includes higher Al content maypossess improved high-temperature oxidation resistance propertiescompared to BSP material 16 with lower Al content. Further, increasingTa content in BSP material 16 may improve mechanical properties of thebraze joint compared to lower Ta content. In particular, Ta maystrengthen the gamma nickel and gamma prime nickel aluminide phases byincreasing lattice mismatches.

BSP material 16 may be formed by mixing an alloy powder or multiplealloy powders in a selected composition, then sintering the powder whiledisposed in a mold to form a sintered preform with reduced porosity. Thesintering temperature and the duration of the sintering may depend atleast in part on the composition of the alloy powder or multiple alloypowders. The mold shape may be selected so that BSP material 16substantially fills repair portion 14 or may be selected to result in aBSP material 16 that may be cut or machined to substantially fill repairportion 14.

In some examples, the sintered powder may then be cut or machined into apredetermined shape. For example, the predetermined shape may correspondto a shape of repair portion 14. As described above, repair portion 14may include a relatively simple geometry as shown in FIG. 1A, or mayinclude a more complex geometry, e.g., as shown in FIG. 1B. Accordingly,the sintered powder may be cut or machined into a relatively simpleshape, or a more complex shape, e.g., including curvature, angles,apertures, three-dimensional surface features, or the like to form BSPmaterial 16. Regardless of the complexity of the shape of BSP material16 and depending upon the geometry of repair portion 14, BSP material 16may include a substantially two-dimensional shape (e.g., a plane) or athree-dimensional shape (e.g., including curvature, planes at angleswith respect to one another, and the like).

By utilizing BSP material 16, alloys with desirable mechanical andchemical (e.g., high temperature oxidation resistance) may be utilizedin a brazing technique to repair damage to base component 12. Theresulting repaired portion may possess sufficient mechanical strengthand high temperature oxidation resistance to be utilized in a hightemperature mechanical system, such as a nozzle guide vane in a gasturbine engine. Further, by utilizing a BSP material 16, the repairedportion may include reduced porosity compared to a joint formed using abraze powder, positioning of the braze material may be easier and moreprecise than with a braze powder, and larger damaged portions may berepaired, including damaged portions that include through-holesextending from a first surface of a base component to a second surfaceof the base component.

FIG. 2 is a flow diagram illustrating an example technique for repairinga damaged portion including a through-hole using a BSP material. Thetechnique of FIG. 2 will be described with reference to repaired article10 of FIG. 1A for purposes of illustration only. It will be appreciatedthat the technique of FIG. 2 may be performed with a different article,or that article 10 may be used in a different repair technique.

The technique of FIG. 2 includes removing a portion of base component 12adjacent to a damaged portion of base component 12 to define repairportion 14 (52). Repair portion 14 includes a through-hole that extendsfrom first surface 22 of base component 12 to second surface 24 of basecomponent 12. Repair portion 14 defines repair surfaces 18 and 20, whichmay be smoother and/or geometrically simpler than the surfaces of thedamaged portion. In some examples, the removed portion of base component12 may be sufficiently large to remove all damage from base component12. In other examples, the removed portion of base component 12 may notremove all damage. For example, the removed portion of base component 12may include any damaged portions that significantly deviate from theoriginal geometry of base component 12, e.g., by protruding from thesurface of base component 12, but may leave smaller damaged areas, suchas smaller cracks that may or may not extend through a thickness of basecomponent.

Although not shown in FIG. 2, in some examples, after removing theportion of base component 12 adjacent to the damaged portion of basecomponent 12 to define repair portion 14 (52), repair surface 18, repairsurface 20, first surface 22, and/or second surface 24 may be inspectedand cleaned. Cleaning may include removing chemically damaged portionsof the surface, e.g., portions of surfaces 18, 20, 22, and/or 24 thatwere burned or oxidized, removing coatings on surface 22 and/or surface24, or the like. The cleaning may be accomplished mechanically,chemically, electrochemically, or the like. For example, one or more ofsurfaces 18, 20, 22, or 24 may be ground, sanded, grit-blasted,chemically mechanically polished, etched, or the like to clean thesurface. The cleaned surfaces may produce a stronger joint to BSPmaterial 16 than uncleaned surfaces.

The technique of FIG. 2 includes forming BSP material 16 tosubstantially reproduce a shape of the through-hole of repair portion 14(54). BSP material 16 may be formed by mixing an alloy powder ormultiple alloy powders in a selected composition, then sintering thepowder while the powder is disposed in a mold to form a sintered preformwith reduced porosity. The sintering temperature and the duration of thesintering may depend at least in part on the composition of the alloypowder or multiple alloy powders. The mold shape may be selected so thatBSP material 16 substantially fills repair portion 14 or may be selectedto result in a BSP material 16 that may be cut or machined tosubstantially fill repair portion 14.

In some examples, the sintered powder may then be cut or machined into apredetermined shape. For example, the predetermined shape may correspondto a shape of repair portion 14, such that BSP material 16 substantiallyfills a width and depth (e.g., a volume) of repair portion 14. Asdescribed above, repair portion 14 may include a relatively simplegeometry as shown in FIG. 1A, or may include a more complex geometry,e.g., as shown in FIG. 1B. Accordingly, the sintered powder may be cutor machined into a relatively simple shape, or a more complex shape,e.g., including curvature, angles, apertures, three-dimensional surfacefeatures, or the like to form BSP material 16. Regardless of thecomplexity of the shape of BSP material 16 and depending upon thegeometry of repair portion 14, BSP material 16 may include asubstantially two-dimensional shape (e.g., a plane) or athree-dimensional shape (e.g., including curvature, planes at angleswith respect to one another, and the like).

The technique of FIG. 2 then includes placing BSP material 16 in repairportion 14 (56). For example, as shown in FIG. 1A, BSP material 16 maybe placed to contact repair surfaces 18 and 20 of repair portion 14. Insome examples, BSP material 16 may be tack welded in place to maintainthe position of BSP material 16 relative to base component 12 prior toheating BSP material 16. For example, BSP material 16 may be tack weldedusing resistance welding.

In some examples, the technique of FIG. 2 may optionally includepositioning additional braze material adjacent to BSP material 16 (58).In some examples, additional braze material may be positioned adjacentto BSP material 16 (58) prior to heating at least the BSP material 16(60). The additional braze material may include a Ni- or Co-based alloy,such as a Ni- or Co-based alloy with a composition substantially similarto that of BSP material 16. The additional braze material may include asecond BSP material, such as a sheet or foil; a braze paste; a brazepowder; or the like. The additional braze material may be positionedadjacent to BSP material 16 to fill or cover parts of repair portion 14or adjacent damage that BSP material 16 does not fill. For example, theadditional braze material may be positioned in cracks or spaces notfilled by BSP material 16, may be placed over BSP material 16,contacting first surface 22 or second surface 24 to provide asubstantially continuous surface after heating, or the like. In someexamples, multiple additional braze materials, such as multipleadditional BSP materials, or an additional BSP material and a brazepaste or powder, may be positioned adjacent to BSP material 16 (58).

In examples in which a braze powder or braze paste are used as theadditional braze material, positioning additional braze materialadjacent to BSP material 16 (58) may include positioning braze stopmaterial at selected locations of base component 12 to retain theadditional braze material at desired locations of base component 12during heating. The selected locations of base component 12 may includeexternal locations (e.g., on an exterior surface), internal locations(e.g., within internal cavities), or both.

The technique of FIG. 2 further includes heating at least BSP material16 to join BSP material 16 to base component 12 and change themicrostructure of BSP material 16 to a brazed and diffusedmicrostructure (60). In some examples, BSP material 16 may be heated ina furnace or other closed retort, and base component 12 may be heatedwith BSP material 16. In some examples, the furnace or closed retort mayenclose a vacuum or substantially inert atmosphere (e.g., an atmosphereincluding constituents that substantially do not react with basecomponent 12 and BSP material 16 at the temperatures and pressuresexperienced by the interior of the furnace or closed retort). In someexamples, BSP material 16 may be heated at a braze temperature ofbetween about 1093° C. (about 2000° F.) and about 1288° C. (about 2350°F.), such as a braze temperatures of about 1260° C. (about 2300° F.).The time for which BSP material 16 is heated at the braze temperaturemay vary from about 10 minutes to about 60 minutes, for example betweenabout 20 to 40 minutes.

In some examples, rather than placing BSP material 16 (56) andadditional (optional) braze material (58) before heating at least BSPmaterial 16 (60), at least BSP material 16 may be heated to join BSPmaterial 16 to base component 12 (60) before additional braze materialis positioned adjacent to BSP material 16 (58). Once additional brazematerial is positioned adjacent to BSP material 16 (58) at least theadditional braze material may be heated to join the additional brazematerial to BSP material 16 and/or base component 12. For example, theadditional braze material may be heated using similar or substantiallythe same heat treatment parameters as described above with reference toBSP material 16.

BSP material 16 then may be allowed to cool to ambient temperature toform a solid and join to base component 12. In some examples, as part ofheating at least BSP material 16 to join BSP material 16 to basecomponent 12 and change the microstructure of BSP material 16 to abrazed and diffused microstructure (60), BSP material 16 may besubjected to a diffusion heat treatment cycle. For example, at least BSPmaterial 16, and possibly BSP material 16 and base component 12, may beheated in a vacuum furnace back filled with argon gas maintaining at apressure between 100 to 800 microns Hg at a temperature between about1000° C. and about 1200° C. for between about 4 hours and about 24hours. For example, between about 1038° C. and about 1149° C. for atleast 17 hours at least BSP material 16, and possibly BSP material 16and base component 12, may be heated in a vacuum furnace back filledwith argon gas maintaining at a pressure between 100 to 800 microns Hgat a temperature between about 1038° C. and about 1149° C. for at least17 hours. The diffusion heat treatment may allow smaller alloyingadditions from the low melt braze powder (e.g., boron and silicon) todiffuse into the adjacent high melt powder in BSP material 16 and intobase component 12 to create a more homogeneous microstructure andincrease the re-melting temperature of the repaired structure.

In some examples, at least BSP material 16 may be machined aftercompletion of heat treatments to remove excess BSP material 16 andrestore base component 12 to a nominal part geometry.

EXAMPLES Example 1

FIGS. 3A-3J are photographs illustrating an example nozzle guide vaneduring various stages of repair of a damaged vane airfoil. As shown inFIG. 3A, the airfoil 64 of nozzle guide vane 62 suffered burn throughdamage 66 on the pressure side 68 of the airfoil 64. FIG. 3B showsnozzle guide vane 62 after removing a portion of airfoil 64 adjacent tothe burn through damage 66 to define a 3/8 inch diameter through-hole70. FIG. 3C shows the airfoil with a BSP material 72 placed inthrough-hole 70. As shown in FIG. 3C, additional cracks 74 are presentin the airfoil adjacent to the repair portion through-hole. FIG. 3Dshows additional braze material in the form of braze paste 76 applied tothe airfoil 64, including within additional cracks 74, with brazestop-off material on the airfoil 64 to maintain the braze paste 76 indesired locations. The braze stop-off material also may be appliedinside airfoil 64, which is not shown in the figures. FIG. 3E shows theairfoil 64 after a first brazing cycle has been completed to join theBSP material 72 and braze paste 76 to the vane airfoil 64, to repairthrough-hole and additional cracks 74 and to change BSP material 72 andbraze paste 76 into a brazed microstructure. FIG. 3F shows twoadditional BSP materials 78 and 80 placed over the repair portion. EachBSP material 78 and 80 in FIG. 3F was about 0.010 inch thick. Theadditional BSP materials 78 and 80 were resistance tack welded to thesurface of the vane airfoil 64. FIG. 3G shows the vane airfoil 64 aftera second brazing cycle to join the additional BSP materials 78 and 80 tothe vane airfoil 64. FIG. 3H shows the locations of the two sectionsshown in FIGS. 3I (section 1) and 3J (section 2). As shown in FIGS. 3Iand 3J, the BSP filled substantially the entire depth of the repairportion through-hole 70 and additional cracks 74.

Example 2

FIGS. 4A-4D are photographs illustrating an example nozzle guide vane 92during various stages of repair of a damaged platform 94. FIG. 4A showsplatform burn-through damage 96. FIG. 4B shows the platform 94 afterremoving a portion of the platform 94 adjacent to the damage 96 todefine a through-hole 98. FIG. 4C shows the platform 94 with a BSPmaterial 100 placed in the through-hole 98 and resistance tack welded inplace. FIG. 4D shows additional BSP material 102 place on a surface ofthe platform over the BSP material 100 in the through-hole 98, afterheating to join the BSP material 100 to the platform 94.

Example 3

FIGS. 5A and 5B are photographs illustrating an example BSP material 114having three-dimensional surface features 116 and a repaired vaneairfoil including the BSP material 114 having the three-dimensionalsurface features 116.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method for repairing an article, the methodcomprising: removing a portion of a base component of the article, thebase component being adjacent to a damaged portion of the base componentto define a repair portion of the base component, wherein the basecomponent comprises a cobalt- or nickel-based superalloy, and whereinthe repair portion of the base component comprises a through-holeextending from a first surface of the base component to an inner surfaceof the base component; forming a braze sintered preform to substantiallyreproduce a shape of the through-hole, wherein the braze sinteredpreform comprises a Ni- or Co-based alloy; placing the braze sinteredpreform in the through-hole; and heating at least the braze sinteredpreform to cause the braze sintered preform to join to the repairportion of the base component and change a microstructure of the brazesintered preform to a brazed and diffused microstructure, wherein thebraze sintered preform comprises three-dimensional surface features on afirst side of the braze sintered preform, wherein the first side of thebraze sintered preform in positioned adjacent the inner surface of thebase component, and wherein the three-dimensional surface featuressubstantially reproduce three-dimensional surface features of thedamaged portion of the inner surface of the base component.
 2. Themethod of claim 1, wherein the article further comprises a secondcomponent defining a surface opposing the inner surface of the basecomponent.
 3. The method of claim 2, wherein the article comprises adual wall component, wherein the base component forms an outer wall ofthe dual wall component, and wherein the second component defines aninner wall with the inner surface opposing the inner surface of the basecomponent.
 4. The method of claim 3, wherein the three-dimensionalsurface features of the braze sintered preform comprise at least one ofa pedestal or a cooling feature, wherein the at least one of thepedestals or the cooling feature substantially reproduce at least one ofa pedestal or a cooling feature of the damaged portion of the innersurface of the outer wall.
 5. The method of claim 2, wherein thethree-dimensional features of the braze sintered preform extend out of asurface plane defined by the inner surface of the base component.
 6. Themethod of claim 2, wherein the article comprises a turbine vane, whereinthe base component defines a first wall of the turbine vane, and thesecond component defines a second wall of the turbine vane.
 7. Themethod of claim 6, wherein the first wall of the turbine vane comprisesone of a suction side airfoil wall or a pressure side airfoil wall, andthe second wall of the turbine vane comprises another of the suctionside airfoil wall or the pressure side airfoil wall.
 8. The method ofclaim 6, wherein the three-dimensional surface features of the brazesintered preform comprise at least one of a pedestal or a coolingfeature, wherein the at least one of the pedestals or the coolingfeature substantially reproduce at least one of a pedestal or a coolingfeature of the damaged portion of the inner surface of the first wall.9. The method of claim 6, wherein the three-dimensional surface featuresof the braze sintered preform extend out of a surface plane defined bythe inner surface of the first wall.
 10. The method of claim 1, whereinplacing the braze sintered preform in the through-hole comprisingplacing the braze sintered preform such that the first side issubstantially parallel to the inner surface of the base component. 11.The method of claim 1, wherein the article further comprises a secondcomponent defining a surface opposing the inner surface of the basecomponent, and wherein the damaged portion of the base component doesnot extend through the second component.
 12. The method of claim 1,wherein the braze sintered preform substantially fills a depth of thethrough-hole.
 13. The method of claim 1, wherein the damaged portion ofthe base component is at least one of airfoil burn-through, platformburn-through, trailing edge burn out, trailing edge burn back, leadingedge burn out, a through crack, a turbine vane internal pedestal damage,or blow-out failure of at least one of a pressure or suction sides of anairfoil.
 14. The method of claim 1, further comprising spot welding thebraze sintered preform in place relative to the base component prior toheating at least the braze sintered preform.
 15. The method of claim 1,wherein the braze sintered preform comprises a substantially homogeneousmixture of a high melt Ni- or Co-based superalloy powder and a low meltbraze powder.
 16. The method of claim 1, wherein the braze sinteredpreform comprises between 0.05 and 0.116 wt. % carbon, between 0.11 and0.376 wt. % silicon, between 8.424 wt. % and 11.640 wt. % chromium,between 0.284 wt. % and 0.835 wt. % boron, between 4.8 wt. % and 5.8 wt.% aluminum, between 2.675 wt. % and 4.232 wt. % tungsten, between 0.650wt. % and 1.362 wt. % molybdenum, between 1.4 wt. % and 2.462 wt. %rhenium, between 7.184 wt. % and 8.942 wt. % tantalum, between 0.690 wt.% and 1.386 wt. % hafnium, and between 8.725 wt. % and 10.964 wt. %cobalt, and nickel.
 17. The method of claim 16, wherein the brazesintered preform comprises a maximum of 0.082 wt. % manganese, a maximumof 0.003 wt. % sulfur, a maximum of 0.013 wt. % phosphorus, a maximum of0.018 wt. % titanium, a maximum of 0.161 wt. % yttrium, a maximum of0.034 wt. % zirconium, a maximum of 0.180 wt. % iron, a maximum of 0.093wt. % vanadium, a maximum of 0.10 wt. % copper, a maximum of 0.007 wt. %magnesium, a maximum of 0.084 wt. % oxygen, a maximum of 0.030 wt. %nitrogen, a maximum of 0.242 wt. % platinum, and a maximum of 0.150 wt.% other elements.
 18. The method of claim 16, wherein the braze sinteredpreform comprises about 0.3 wt. % silicon, about 10.2 wt. % chromium,about 0.6 wt. % boron, about 5.2 wt. % aluminum, about 3.3 wt. %tungsten, about 0.9 wt. % molybdenum, about 1.8 wt. % rhenium, about52.1 wt. % nickel, about 0.2 wt. % niobium, about 8.1 wt. % tantalum,about 1.0 wt. % hafnium, and about 9.6 wt. % Co.
 19. The method of claim16, wherein the braze sintered preform comprises about 0.2 wt. %silicon, about 8.6 wt. % chromium, about 0.3 wt. % boron, about 5.7 wt.% aluminum, about 4.1 wt. % tungsten, about 1.2 wt. % molybdenum, about2.3 wt. % rhenium, about 52.2 wt. % nickel, about 0.1 wt. % niobium,about 7.3 wt. % tantalum, about 1.2 wt. % hafnium, and about 10.7 wt. %Co.
 20. The method of claim 1, wherein heating at least the brazesintered preform comprises heating at least the braze sintered preformin a vacuum furnace at a temperature between about 1093 degrees Celsiusand about 1260 degrees Celsius.